Low field magnetoresistance of La0.7Ca0.3MnO3 ceramics fabricated by fast sintering process

Bulk perovskite manganese oxide La0.7Ca0.3MnO3 was prepared in 2 min by a novel densification method based on self-propagating reactions. The influence of temperature on the structure and transport properties has been investigated. The structures of specimens were analyzed using the Rietveld refinement technique and the specimens are observed to have orthorhombic structure with Pbnm space group. Moreover, study of magnetic transport properties reveals that the variation of the magnetization values and the Curie temperature is attributed to grain size and oxygen deficiency concentration at different sintering temperatures. In the plot of resistivity as a function of temperature, double metal-insulator transitions accompanied with a single ferromagnetic transition are observed, which is explained on the basis of inhomogeneous oxygen generated by the nonuniform temperature field. The enhanced low-field magnetoresistance (LFMR) is achieved, suggesting that it is an efficient way to obtain LFMR of La0.7Ca0.3MnO3 specimens. We explained the enhanced low field magnetoresistance by the spin-polarized tunneling model on the relaxation grain boundary induced by this ultra fast sintering process.

► Bulk La0.7Ca0.3MnO3 ceramics can be prepared by a new densification method based on self-propagating reactions.
► Effect of sintering temperature on the structure and the transport properties has been investigated.
► Rietveld analysis has been performed to refine the structures.
► Enhanced low field magnetoresistance is achieved.